In residential and commercial construction, drainpipes are used to direct waste from a sink, toilet or drain, into the sewer below. In order to locate a sink, toilet or drain on a concrete floor, a pipe riser is first installed prior to pouring of the concrete. The pipe riser, following the pouring of the concrete floor, usually extends several inches or more above the level of the floor. The level of the pipe riser is then brought even with the floor, or to a level which is somewhat recessed below the level of the floor. The final plumbing work is then completed.
In the case of a conventional toilet, shower drain, floor drain, and floor mounted clean out, an annular recess is required in the floor. The annular recess is concentric with the pipe riser, in order to provide a space for a water closet connecting collar to be secured to the upper end of the pipe.
The prior art includes a number of devices developed to reserve the annular recess about the pipe riser. These devices, however, tend to be relatively expensive and cumbersome. For example, U.S. Pat. No. 5,099,887, issued Mar. 31, 1992 to O. F. Hooper, discloses a collar for a pipe riser for maintaining an annular space about the periphery of the riser during the pouring of the floor. This construction involves inner and outer sleeves separated by a plurality of knock-out webs. The inner sleeve snugly receives the upper end of the riser, while the outer sleeve maintains an annular space about the riser. After the floor is poured and solidified, the webs are knocked out and the inner sleeve is removed along with the webs.
Another example of a prior art device is disclosed in U.S. Pat. No. 3,421,551, issued Jan. 14, 1969 to G. F. Currier. This patent is directed to a spacing sleeve for close fit about the upper end of an upright water closet drainpipe, to provide an annular recess about the pipe in a concrete floor. The sleeve is a one-piece right cylindrical member formed from a polystyrene expanded plastic foam which has a high compressive strength, will not absorb water, and is readily frangible or breakable. In use, after the floor has been poured, the inner portion of the frangible sleeve is compressed and broken away by hand, thereby clearing an annular cavity about the upper end of the pipe.
Still another example is shown in Canadian Patent No. 2,026,420, issued Nov. 26, 1996 to D. K. Pollard. This patent discloses a sleeve that is placed over and cemented to a pipe end. The sleeve is complex-shaped and it involves time-consuming and complex installation.
In view of the complexity of the collar disclosed in U.S. Pat. No. 5,099,887, the easily damaged nature of the collar disclosed in U.S. Pat. No. 3,421,551, and the complexity of the shape and installation of the sleeve disclosed in Canadian Patent No. 2,026,420, there is a need for a simple, recess-reserving device of sufficient strength for use in maintaining a space around a pipe riser.